Mushrooming projectiles



Oct. 9, 1956 H. E. FRECH, JR 2,755,738

MUSHROOMING PROJECTILES 'Filed July 27, 195o INVENTOR..

HARRY E.FRECH JR:

ATTORNEYS.

Mttsrmootnnso rnotncrrtns Harry E. Frech, r., University City, Mo., assigner to Olin Mathieson Chemical Corporation, a corporation of Virginia Application July 27, 195i), Serial No. 176,152

7 Claims. (Cl. 102-91) This invention relates to projectiles, and more specifi cally to projectiles of the expanding or mushrooming type for small caliber firearms, and to a method of making an improve projectile of this type.

Mushrooming or expanding bullets for small caliber firearms (i. e., sporting rifles and hand guns as distinguished from pieces which are tired from mounts, vehicular or otherwise) normally consist of a soft core and a harder metal jacket. This harder metal jacket can completely enclose the softer core, or can be a compound jacket with one jacket covering only the pointed or nose end of the core and the other jacket, normally referred to as the base jacket, covering the remainder of the core. In another type of mushrooming bullet only a base jacket is used, so that the nose or pointed end of the softer core protrudes from this jacket.

The base jacket of such a mushrooming bullet is commonly fabricated from a suitable disk of metal by a series of forming and drawing operations. In fabricating the base jacket for a .3d-4() Krag bullet, for example, a disk of suitable dimensions is cut or blanked from a strip of the desired metal, and subsequently formed into a cupshaped article by passing through a die while on a punch. Normally the disk is formed into the cupshaped article in one operation. The diameter and wall thickness of this cup are subsequently decreased, while the depth or length of the cup is increased, in a series of drawing operations.

Various means for improving the mushrooming characteristics of jacketed bullets have been suggested heretofore, including pleating the wall of the jacket, slitting the wall of the jacket, and providing a serrated edge at the mouth of the jacket. While each of these expedients provides more or less weakened lines along which the jacket is intended to tear when the projectile strikes its objective, various difficulties have been encountered with bullets of this character in that those with the pleats or slits are so weakened that the forming operations, after the insertion of the core, frequently impair the ballistic characteristics of the projectile, while those with the serrated mouth do not mushroom with uniformity. Moreover, each of the expedients heretofore suggested has olferend dimculty in the assembling operation with separate tips, it being practically impossible to achieve such continuity of streamlining at the joint between the base jacket and the tip that the ballistic properties of the composite projectile are not impaired.

The object of the present invention, generally stated, is to provide a base jacket which will consistently and regularly mushroom, and which may be used with af*- vantage either alone, as in a soft point bullet, or with a nose jacket or tip.

Other objects will become apparent to those skilled in the art when the following description is read in connection with the accompanying drawings, in which:

Figure l is an amal sectional view of a drawn cup representing the base jacket of the present invention at one stage of its manufacture, in correlation with a side elevalatented Oct. 9, 1956 tion of a portion of a drawing punch for thus forming the jacket;

Figure 2 is a sectional view taken along line 2 2 of Figure l, omitting the punch;

Figure 3 is an axial sectional view in correlation with a side elevation of a drawing punch used in the formation of the same;

Figure 4 is a sectional view taken along line 4 4 of Figure 3, but omitting the drawing punch;

Figure 5 is an enlarged detail View of a section of Figure 4;

Figure 6 is a side elevation, part being in section, of a jacketed projectile constructed in accordance with the present invention; and

Figure 7 is a perspective view of a mushroomed projectile of the character shown in Figure 6.

In accordance with this invention, a projectile having improved mushrooming characteristics is obtained by creating a plurality of axially extending, circumferentially spaced metallurgical notches in the wall of the base jacket. By metallurgical notch is meant that the member, although of substantially uniform dimension, has axially extending lines or sections which have different physical properties from intervening sections, by virtue of different degrees of cold-work performed upon them. For example, the metallurgical notches may be formed during the fabrication of the jacket by drawing with a punch of polygonal cross-section (thus producing, at this stage, a jacket whose wall is not of uniform dimension), annealing, and then drawing the jacket again with a round punch. Such procedure produces a jacket of uniform wall thickness, but with a variation in the amount of coldwork performed, and consequently results in section or lines of different strength. When an assembled bullet comprising such a jacket and a core, with or without a tip, is fired, the point of the bullet expands in diameter upon impact, and the expansion continues beyond the juncture of the base jacket and the point. rl`l1e presence of the metallurgical notches, running in a general axial direction and spaced about the circumference of the bullet, causes the jacket to split in the region of the metallurgical notches during the process of expansion upon impact, and thus greatly increases the ease and uniformity of expansion and reduces the possibility that the jacket may fail to expand. At the same time the uniformity of jacket tearing keeps the loss of the core to a minimum.

in the fabrication of the base jackets in accordance with the present invention, the usual procedure of blanking and cupping from a strip of the desired vmetal is followed. Any desired number of drawing operations may be performed upon the cup, but, in accordance with the present invention, one of these drawing operations prior to the last, and preferably next to the last, is performed with a punch having a polygonal cross-section, preferably hexagonal or octagonal. After annealing, the final draw upon the cup is made, however, with a punch which is circular in cross-section, so that uniform wall thickness is ultimately achieved. The drawing of the cup into circular section after it had previously been drawn into an internally polygonal, exteriorly circular section yproduces a variation in the cold-work upon the metal, in

that the metal ows lengthwise away from the sections which were thickest after the polygonal draw, thus producing the severely cold-worked metallurgical notches, or weaknesses, approximately midway between the corners of the polygon. The final interiorly circular configuration of the jacket permits its ready assembly with the core and a tip or tip jacket, if desired, and its ready conformation with the other parts to the shape desired for ballistic purposes.

Referring now to the vdrawings for an illustrative embodiment of the invention, a base jacket 1, after `being preliminarily formed to cup shape, is drawn on a punch 2, part of whose exterior surface is octagonaily shaped, so as to provide ats 3 with corners 4 therebetween. Drawing the preliminarily formed cup upon such a punch results in the cup assuming an interior configuration corresponding to the exterior configuration or the punch, so that the jacket 1 has ats 13 and corners t4 therebetween as eay shown `in tgure the wam \t`1i\c\\.hess"be\\hg less at the corners 14 than between them. in the drawing operation with the polygonal punch, the length of the cup is increased by the ow of metal away from the regions adjacent corners 14, the thickness at the midsection of ats 13 remaining substantially unchanged.

After the jacket 1 has been drawn by punch 2, it is preferably annealed to relieve the stresses therein, in accordance with conventional annealing techniques for the alloy involved. Such annealing more or less erases the effect of the unequal cold-work accomplished by punch 2. The jacket is then subjected to another drawing operation wherein a punch 5 of the circular cross-section is ernployed. The punch 5 effects an elongation of the jacket 1, and reduces the thickness at the flats 13 to substantially that which punch 2 produced at the corners 14. so that uniform wall thickness, with circular interior and exterior shape, is provided where the ats 13 and corners 14 existed previously. The jacket is not annealed after the final draw.

After being drawn upon a circular punch 5, a crosssection of the jacket 1, taken in the region where the ats 13 and corners 14 previously existed, reveals a striking difference between the crystal structure at sections 24 (which correspond to ythe location of the corners 14) and the intermediate sections 23 (which correspond to the location of the ats 13). The crystal structure between 'two sections 24 and the intervening sections Z3 is shown in detail in Figure 5, where it will be observed that the crystals in section 24 are oriented so that the crystals appear to run in the radial direction, whereas in the adjacent sections 23 (where the metal has been severely cold-worked since annealing) the crystals are oriented so that they appear to run in the circumferential direction. The contrast between the crystalline arrangement in sections 23 and 24 is clearly shown by the photomicrograph on the next page, wherein the central portion corresponds to the intermediate section 23 of Figure 5 and is the region whereat (because of the localized cold-working without subsequent anneal) the ductility and resistance to rupture is less, and the brittleness greater, than in the regions which have not been so severely coldworked since annealing. Consequently, the splitting of the jacket upon impact occurs at about the middle of the photomicrograph.

After the base jacket 1 is drawn, as above described, the mouth thereof may be cut off at 6, thus providing a smooth, regular mouth line. The jacket may then be assembled with a core 7, and operated upon in suitable dies to conform `the point of the core and the mouth 6 of the jacket to `the desired shape. While the projectile is shown as a soft point bullet, it will be understood that any suitable separate tip, or separate tip jacket, may be provided upon it without difliculty, particularly because the interior configuration of the jacket 1 at its mouth 5 is circular and regular.

Figure 7 shows a projectile, jacke-ted in accordance with the present invention, after it has been tired into live feet of water. 'lt is evident that, as the core 7 expanded, the jacket 1 split so as to form a series of leaves S. The splitting occurs along lines about midway of the respective sections 23.

In. comparative tests with other jacketed projectiles whose jackets had been operated upon to improve their mushrooming characteristics, projectiles ofthe present invention consistently showed substantial advantage. For

example, a 180 grain .SO-40 Krag soft point bullet jack- 4 eted in accordance with this invention, when fired into live feet or" water at a range of fifty yards, mushroomed so as to increase its diameter by 114 percent of its original diameter; at one hundred yards by 111 percent; and at two hundred yards by 91 percent, while jacketed projectiles of commerce (constructed as shown in Figure 2 of United States Patent No. 2,327,950) showed increases in cent, and 43 percent. The percentages given represent the averages from the firing of ten rounds of each projectile at the respective ranges.

A similar series of comp-arative tests was carried out with a .300 Savage grain soft point bullets fired into ve feet of water. rojectiles embodying base jackets made in accordance with the present invention exhibited an increase in diameter of 108 percent, 106 percent, and 54 percent at ranges of iifty, one hundred, and two hundred yards, respectively, while the projectiles of the same commercial type above referred to exhibited increases in diameter of 54 percent, 47 percent, and 38 percent at the respective ranges.

From the foregoing description, those skilled in the art should readily understand that the invention accomplishes its objects, and provides a method of improving the mushrooming of jacket-ed bullets whereby the advantageous results may be accomplished without the expense of special operations for the purpose, and, further, that the desirable mushrooming is accomplished without malformation of the mouth of lthe base jacket, or otherwise interfering with the conventional assembling and shaping operations wherein the base jacket, the core, and the tip or tip jacket, if any, are concurrently operatedV upon.

While one complete embodiment of the invention has been disclosed in detail, it is obvious that many variations in the procedure and in the shapes of the tools will present themselves to those skilled in the art without departing from the spirit of the invention. For example, the punch, hereinbefore described las polygonal, need not be truly polygonal, so long as the internal punch is so coordinated with the companion external die that thin sections or lines are formed in the jacket during some draw prior to the last; and then, when the jacket is given its nal draw, the wall section is reduced to uniform thickness. Moreover, instead of using a polygonal punch with a circular die for lthe one drawing operation, as above described, the jacket may be drawn with a circular punch and a polygonal die.

Consequently it Iis to be distinctly understood that the invention is not limited to the details of the foregoing disclosure, save as indicated in the appended claims.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

1. In the art of making jacketed bullets wherein a cup of cold-drawable metal is formed to jacket shape by successive draws, the improvement which comprises, drawing the cup to a cross-section having alternate thick and thin regions, annealing the cup, thereafter cold drawing the cup to a cross-section of uniform thickness, and then, while the physical properties resulting from the lastmentioned drawing operation remain non-uniform, assembling the cup with a soft metal core and shaping the composite bullet.

2. In the art of making jacketed bullets wherein a cup of cold-drawable metal is formed to jacket shape by successive draws, the improvement which comprises, drawing the cup to a shape wherein one of the interior and exterior peripheral walls is polygonal in cross-section and the other thereof is circular, annealing the cup, thereafter cold drawing the cup to a cross-section wherein the interior and exterior walls are substantially concentric and circular, and then, while the physical properties resulting from the last-mentioned drawing operation remain nonuniform, assembling the cup with a soft metal core and shaping the composite bullet.

3. The process of claim 2 wherein the wall which is drawn to the polygonal shape is the interior Wall.

4. A base jacket for a small caliber mushrooming bullet, said jacket having a forward portion adapted to split upon impact, said forward portion having a wall which at each circumferential increment is uninterrupted and uniformly thick, and the wall of said forward portion having circumferentially spaced axially extending regions of less ductility than the intervening regions.

5. In a small caliber mushroom projectile having a core and a base jacket, the improvement which comprises, said base jacket being of the same metal throughout and of substantially uniform wall thickness throughout a circumferential section adjacent its mouth, and the metal of said wall at said section having circumferentially spaced axially extending regions of different physical properties from the metal intervening axially extending said regions.

6. In a mushroom projectile having a soft metal core and a base jacket of cold-drawable metal, the improvement which comprises, said base jacket having a series of circumferentially spaced axially extending sections which have been cold-worked to a greater extent `than the intervening sections, and in which, as a result of such non-uniform cold-working, the resistance to tear in the first-mentioned sections is different from the resistance to tear in the intervening sections.

7. In a base jacket for small caliber bullets of the mushrooming type wherein the jacket is formed of cold-drawable metal with a mouth at one end and a region adjacent the mouth is weakened at cireumferentially spaced intervals to facilitate splitting upon impact with a target, the improvement which comprises, said base jacket being of circumferentially uniform thickness and being circumferentially uninterrupted, said base jacket having circumferentially spaced axially extending sections which have been cold-worked to a greater extent than the intervening axially extending sections, and in which, as a result of such non-uniform cold-working, the resistance to tear is substantially different in said spaced axially extending sections from in said intervening axially extending sections.

References Cited in the le of this patent UNITED STATES PATENTS 45,985 Estabrook Ian. 24, 1865 1,099,298 Hoagland June 9, 1914 1,303,727 Rice May 13, 1919 1,715,788 Rousseau June 4, 1929 2,044,780 Hardigg June 23, 1936 2,183,502 LeFere Dec. 12, 1939 2,325,079 Soderholrn July 27, 1943 2,327,950 Whipple Aug. 24, 1943 2,333,091 Crasnoi Nov. 2, 1943 2,338,652 Lefere Ian. 4, 1944 

